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As originally designed, the UMP is chambered for larger cartridges (.45 ACP and .40 S&W) than other submachine guns like the MP5, to provide more stopping power against unarmored targets (with slightly lower effectiveness at longer range) than the MP5 (largely offered in 9×19mm, albeit with short-lived production of 10mm Auto and .40 S&W variants). A larger cartridge produces more recoil, and makes control more difficult in fully automatic firing. To mitigate this, the cyclic rate of fire was reduced to 650 rounds/min (600 rounds/min for the UMP45), which makes it one of the slower firing submachine guns on the market.[4]

The UMP9 (the 9×19mm version of the UMP) is almost 0.2 kilograms (0.44 lb) lighter than its MP5 counterpart. Its predominantly polymer construction reduces both its weight and the number of parts susceptible to corrosion.[4][5]

The UMP is available in four trigger group configurations, featuring different combinations of semi-automatic, 2-round burst, fully automatic, and safe settings. It features a side-folding buttstock to reduce its length during transport. When the last round of the UMP is fired, the bolt locks open, and can be released via a catch on the left side. The standard viewing sights are composed of an aperture rear sight and a front ring with a vertical post. It can mount four Picatinny rails (one on top of the receiver, and one on the right, left, and the bottom of the handguard) for the attachment of accessories such as optical sights, flashlights, or laser sights. Vertical fore-grips can be attached to the bottom rail for increased control during burst and automatic fire.[4]

There are three versions of the UMP: the UMP45, firing a .45 ACP cartridge; the UMP40, firing a .40 S&W cartridge; and the UMP9, firing a 9×19mm Parabellum cartridge. Apart from the different chambering, all versions feature the same basic design, the most noticeable difference being the curved magazine used on the UMP9 (whereas the UMP40 and UMP45 use a straight magazine). All three versions of the weapon can be converted to any of the available chamberings via replacement of the bolt, barrel, and magazine.[4][5]

The USC or Universal Self-loading Carbine is a semi-automatic version of the UMP that is available to private citizens. It was designed following the Assault Weapons Ban of 1994 in the United States and was introduced in 2000. Changes from the original UMP include a "thumbhole" type stock and grip (versus the pistol grip of the UMP, though aesthetically there is little difference), longer barrel (no flash suppressor), limited 10-round magazine, and semi-automatic only trigger group and action.[6] Originally available in gray, as of 2008 the USC comes only in an all-black finish.[7] In 2013, the USC was cancelled.[8]